Superheater element



April 29, 1941.

A. HUET 22403.72

SUPERHEATER EUEMENT Filed June 4, "1940 I INVENTOR. ANDRE Hu: 7.

ATTORNEY.

Patented Apr. 29, 1941 SUPEEHEATE-R ELEMENT Andre Huet, Paris, FranceApplication June 4, 1940, Serial No. 338,718 In France May 25, 1939 1Claim.

The present invention relates to improvements in tubular super-heatingelements intended to be disposed in the flues of aboiler and moreparticularly in a locomotive boiler.

In locomotive super-heater elements wherein the steam in saturated statepasses rearwardly to the neighborhood of the firebox of the boiler by atube, or assembly of tubes, which will be referred to as the inlettubes, and then flows forwardly through a tube herein called the outletube which extends back towards the superheater header, the outlet tubecontains steam at higher temperature than the inlet tube or tubes andconsequently is submitted to linear displacement greater than that ofthe inlet tubes. This difference of distortion or expansion isaccentuated when the outlet tube is disposed nearly in the axis of theflue; also, when, because of the disposition of the inlet tubes, ortheir shape, or both, the outlet tube is shielded against cooling thatwould otherwise result from radiation of heat in a direction towards thesurface of the flue.

Because of these differences of expansion the outlet tube during use ofthe superheater exerts on the inlet tube or tubes a considerable forcesusceptible of surpassing the elastic limit of the inlet tubes at thetemperature of operation and to produce in these tubes a permanentelongation. When during subsequent cooling of the superheater the outlettube reverts to its normal length the inlet tube remains extendedbecause of having been subjected to permanent elongation. Thus, it issubmitted to a pressure at its extremity with the possibility ofpermanent distortion. The repetition of phenomena of this natureproduces substantial deformation in the inlet tubes which can causeobstruction in the flue, render difllcult the extraction and reinsertionof the superheating elements and eventually renders the superheaterelements useless.

The consequence of these differences of expansion are particularly to befeared when the part of the inlet tubes located in the flue is made upof a series of parts, some of which are more rigid than others, becausethen the deformation is produced in the less rigid parts, flexing thesemore than if the deformation were distributed over the entire length ofthe elements located in the flue.

An object of the present invention is to provide a superheating elementso formed as to alleviate these disadvantages.

According to the invention the inlet tube, or each of the inlet tubes ofa superheating element, is provided with an expansion bend in one of itsless rigid parts, preferably that part which is at least heated. Whenpossible the expansion bend is formed in a part of the inlet tubelocated outside of the flue. This expansion bend lends itself to themovements in question without being submitted to permanent deformationand at the same time to not obstruct the natural path of the gases inthe flue.

This bend may, according to the invention, be formed in one or inseveral :planes and even have the form of a helix.

In elements consisting of several inlet tubes arranged in a circle andgrouped about the outlet tube the expansion bend is formed in portionsof the inlet tubes located outside the flue in the boiler smokebox.

Where the space in the smoke box does not provide room for expansionbend in the inlet tube of the element it may be located in the flue inthe form of a spiral so .alined with other parts of the inlet tubes asto create the least possible obstruction to the gases.

In the drawing:

Figure 1 is a longitudinal sectional view through a boiler flue showinga superheating element embodying the invention.

Figure 2 shows the same element in plan view.

Figures 3 and 4 are sections on the lines 3-3 and 4-4 in Fig. 1.

Figures 5 and 6 are views similar to Figs. 1 and 2 of another type ofsuperheating element embodying the invention.

Figure 7 is a sectional view on line 1-! in Fig. 5.

In the superheater represented in Figs. 1 to 4 the outlet tubes consistof a series of small tubes provided with longitudinal fins and disposedabout a larger outlet tube. The numeral l designates a flue of alocomotive boiler in which are located the assembly of small tubes 2provided with longitudinal fins 3 as well as the large outlet tube i.These tubes are joined together at their inner ends by a bree-ches piece5. At their opposite ends the small tubes 2 are connected by a breechespiece ii to a section I connected to the saturated steam header whilethe outlet tube t has an extension 3 for discharging the superheatedsteam into the superheated steam headers. The position of the headers isfixed with respect to front tube sheet It] of the boiler.

As a general rule the fins 3 do not extend to the breaches piece 5, theend portion of the small tubes 2 near the firebox being exposed to gasesat very high temperature in which it is now useful to increase theabsorption of heat and where the fins could not be sufficiently cooledby the steam. It follows that under the influence of differences ofexpansion which have been mentioned previously, the permanentdeformation of the small tubes are localized, especially when thesetubes are not provided with curves of expansion in this portion near thebreeches piece 5 where the metal is veiy hot.

In a superheater element according to the invention the small tubes 2are provided with an expansion bend 9 located between the front fluesheet and the breeches piece 6. This bend accommodates the elasticdeformation sufficiently to permit the small tubes 2 to follow the largetube 4 in its expansions without being subjected to permanentelongation. As the bends 9 are more easily deformable than the otherparts of the tubes 2, it is these portions that become subjected topermanent deformations, if any should be produced by improvidentcircumstances such as excessive temperature. As shown in Figs. 1 and 2,the bends in the four tubes 2 are located with respect to the axis ofthe flue outlet in such manner as not to block it and thus leave a freepassage for the gases leaving the tube.

In a superheating element represented by Figs. 5 to '7 the saturatedsteam lead is connected by a breeches piece H to two small tubes l2joined at two diametrically spaced points to an annular conduit l3 fromthe other end of which extend the two small tubes I4 joined by abreeches piece 15 to the outlet tube 4 which is disposed substantiallycoincident with the axis of the annular conduit I3. The small tubes I2in portions located in front of the tube sheet are formed with expansionbends. Here again the bent portions are so spaced as not to block theflue outlet, but contrary to the preceding case where each bend is in aplane, here they have been given a twist of to increase theirflexibility.

What I claim is:

In a tubular heat exchange: superheater element disposed in the flue ofa fire tube boiler and having a, plurality of inlet sections joinedoutside the flue by a breeches piece and disposed about an outletsection for superheated steam, said inlet and outlet sectionscommunicating at their inner ends and their outer ends: being rigidlyconnected to saturated and superheated steam headers, respectively; andexpansion bends formed in each inlet section from portions thereofcontiguous to said breeches piece.

ANDRE I-IUET.

